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Replacing values in a data frame conditionally is the process of allowing a user to selectively replace values in a data frame with different values based on specific conditions that the user defines. This can be done by using the ifelse statement, which will check for a specified condition and then execute the code for either the “true” or “false” result. Using this statement, a data frame can be manipulated to replace values that meet a certain condition with a new value.
You can use one of the following methods to replace values in a data frame conditionally:
Method 1: Replace Values in Entire Data Frame
#replace all values in data frame equal to 30 with 0 df[df == 30] <- 0
Method 2: Replace Values in Specific Column
#replace values equal to 30 in 'col1' with 0 df$col1[df$col1 == 30] <- 0
Method 3: Replace Values in Specific Column Based on Another Column
#replace values in col2 with 0 based on rows in col1 equal to 30 df$col2[df$col1 == 30] <- 0
The following examples show how to use each method in practice with the following data frame:
#create data frame
df <- data.frame(team=c('A', 'A', 'B', 'B', 'B'),
points=c(99, 90, 90, 88, 88),
assists=c(33, 28, 31, 30, 34),
rebounds=c(30, 30, 24, 24, 28))
#view data frame
df
team points assists rebounds
1 A 99 33 30
2 A 90 28 30
3 B 90 31 24
4 B 88 30 24
5 B 88 34 28
Method 1: Replace Values in Entire Data Frame
The following code shows how to replace all values equal to 30 in the data frame with 0:
#replace all values in data frame equal to 30 with 0 df[df == 30] <- 0 #view updated data frame df team points assists rebounds 1 A 99 33 0 2 A 90 28 0 3 B 90 31 24 4 B 88 0 24 5 B 88 34 28
Method 2: Replace Values in Specific Column
The following code shows how to replace all values equal to 90 in the ‘points’ column with 0:
#replace all values equal to 90 in 'points' column with 0 df$points[df$points == 90] <- 0 #view updated data frame df team points assists rebounds 1 A 99 33 30 2 A 0 28 30 3 B 0 31 24 4 B 88 30 24 5 B 88 34 28
Method 3: Replace Values in Specific Column Based on Another Column
The following code shows how to replace the values in the ‘points’ column with 0 where the value in the ‘team’ column is equal to ‘B.’
#replace all values equal to 90 in 'points' column with 0 df$points[df$team == 'B'] <- 0 #view updated data frame df team points assists rebounds 1 A 99 33 30 2 A 90 28 30 3 B 0 31 24 4 B 0 30 24 5 B 0 34 28
The following tutorials explain how to perform other common operations in R: